The present invention concerns a fluid distribution system for a variable-crown roll adjustable in zones, this roll comprising a stationary central axle and a revolving roll mantle arranged on the axle, hydraulic loading elements acting upon an inner face of the roll mantle, or a corresponding pressure-fluid chamber, or a series of chambers being provided in a space between the central axle and the mantle. The axial profile of the variable-crown roll can be adjusted by means of these elements or chambers. Furthermore, the fluid distribution system in this roll comprises a system of fluid distribution ducts provided in connection with the central axle. The distribution system is arranged to supply through the same at least pressure fluid passing to the zones of the roll.
Several different adjustable-crown rolls for paper machines or paper finishing equipment are known in the prior art, for which different designations are used such as variable-crown rolls, rolls adjustable in zones, and equivalent terminology. As a rule, these rolls comprise a massive or tubular, stationary roll axle and a roll mantle arranged to revolve about the axle. Between the axle and the mantle, arrangements of glide shoes and/or a chamber of pressure fluid or a series of chambers acting upon an inner face of the mantle, are positioned so that the axial profile of the mantle at the nip can be aligned or adjusted as desired.
In variable-crown rolls, a complicated fluid distribution system is required because the roll includes several points to which fluid must be passed. Such points include zones in a variable-crown roll to which pressure fluid must be passed, various points that require lubrication to which lubrication oil is passed, possible means for the heating of the roll for the supply of heating fluid, and corresponding points that consume fluid. Since a roll includes a great number of different fluid-consuming points, the roll must naturally also have a system of ducts for the outlet fluid. In the prior art, the system of fluid distribution ducts had been formed in a variable-crown roll in a number of alternative ways.
One prior art solution is described, e.g., in U.S. Pat. No. 4,222,324, in which an axial bore of its own has been formed into the axle of the variable-crown roll for each zone of the variable-crown roll, the fluid being passed into the zones out of the bore through radial bores. Thus, it has been necessary to make a considerably high number of bores and provide various pipe systems in such a roll. This results in the drawbacks that cost of manufacture of the system of fluid distribution ducts is quite high, and the system of ducts requires very careful workmanship, since various rubbish, dirt, machine cuttings, and equivalent tend to remain in the ducts. Moreover, it has been necessary to form bores of their own into the roll axle for possible heating and lubrication of the roll, or the roll has had to be provided with a separate system of ducts for these functionings.
Another prior art solution is described, e.g., in DE Patent No. 28 47 029, in which construction an axial bore of large diameter has been formed into the roll axle, with a series of pipes being fitted into this bore and comprising a number of pipes through which the pressure fluid is passed to the hydrostatic loading elements placed in the zones of the roll. The pipe series is connected with a number of sealing elements, by means of which the series of pipes is sealed relative to the axial bore in the axle between the zones. One of the considerable drawbacks of this arrangement is that the pipe series comprises a number of sealing points, and consequently comprises a number of seals. Moreover, the pipes included in the series of pipes must be of very high quality in order to endure the pressures required by the zones. Additionally, these drawbacks have the consequence that the construction of the DE patent structure is extremely expensive and difficult to manufacture. Also, such a solution requires separate systems of ducts, e.g., for possible heating of the roll and for the objects that require lubrication therein.
A further prior-art solution is described, e.g., in U.S. Pat. No. 4,106,405. In the solution described in this document, a central hole of large diameter has been formed into the roll axle, with coaxially-arranged pipes being fitted in this hole through which pressure fluid is fed into the zones of the roll. This solution also involves a number of various drawbacks of which it might be noted that, e.g., the wall thickness of the pipes have to be large because the pressures required by adjoining zones may quite essentially differ from one another. Thus, the risk of buckling of the pipes is quite high. The sealing of the pipes in this solution is also quite doubtful, since the pipes must be sealed relative to one another on the one hand, and must be sealed relative to the central hole formed into the roll axle on the other hand. Thus, such a fluid distribution system is difficult and expensive in view of the manufacture. In this system as well, the roll must be provided with a separate fluid distribution system for possible heating of the roll.